Field of the Invention
The invention relates to the general field of the positioning of attachment members on positioning and centering pins for ophthalmic lenses in order to subsequently attach these positioning and centering pins to these lenses, and the invention concerns in particular the systems comprising such a positioning and centering pin, such an attachment member and a tool for positioning the attachment member on the positioning and centering pin, and groups of such systems.
The invention also relates to methods for positioning such attachment members on such positioning and centering pins.
Description of the Related Art
The invention also concerns machines for positioning ophthalmic lenses on and attaching them to such positioning and centering pins.
It is known that ophthalmic lenses undergo various manufacturing steps. The manufacturing processes generally employed to obtain a finished lens trimmed to the shape of a particular frame typically comprise steps in which the surface of the ophthalmic lens is provided with marks.
Moreover, whether for marking steps or for manufacturing steps as such, for instance surfacing (for example machining) or finishing (for example trimming), the ophthalmic lenses must be held in a given position and be centered with respect to a given positioning reference.
For this purpose, it is common to use centering and positioning pins which are attached to the ophthalmic lenses by virtue of attachment members, the latter being formed for example by adhesive pads.
Prior to the attachment of the pin to the lens via the attachment member, the latter is itself attached to the pin and this attachment is generally carried out by manual positioning of this attachment member on the pin.
This manual positioning is by nature random, relative to a given correct position, and can cause problems during the following steps.
Specifically, incorrect positioning of the attachment member on the positioning and centering pin can result in incorrect positioning of the positioning and centering pin on the lens and thus cause the lens, for example during trimming, to move in rotation (alone or together with the attachment member) with respect to the positioning and centering pin, in other words bring about a misalignment for example on account of shearing of the attachment member during the trimming of the periphery of the lens.
Moreover, incorrect positioning of the positioning and centering pin on the lens on account of incorrect positioning of the attachment member on the positioning and centering pin can conceal the previously made marks, these being necessary for example for correctly positioning the lens on a trimming machine.
These marks may be formed by etchings that represent points or crosses and identify a particular point (for example the optical center of the ophthalmic lens or the prism reference point for a progressive lens), or axis lines (for example for indicating the horizontal axis along which astigmatism is corrected), or shapes delimiting a particular zone (for example a near vision zone or a far vision zone in the case of progressive ophthalmic lenses).
The positioning of the lens on the positioning and centering pin, and consequently the prior positioning of the attachment member on the positioning and centering pin, for the purpose of carrying out a trimming step, is rendered particularly complicated on account of the large number of spectacle frames having different shapes, necessitating multiple sizes of the positioning and centering pins and multiple sizes of the attachment members.
Correctly positioning an attachment member on a positioning and centering pin is thus complex.